The data on the kinetics, selectivity, KIE and the effect of the medium acidity on the rate of reactions of benzene and alkylbenzenes in sulfuric acid (59-78 mass % H2SO4) solutions of 1-adamantanol at 30 oC testify about adamantyl (Ad+) carbocations are straightforward reagent, alkylating arenes; orto-position of benzene ring are not accessible because of steric hindrances; attack rate by Ad+ cation accessible para- and meta-positions of ring is controlled by formation of σ-complex.